Routers could become targets of DOS attacks

Denial-of-service attacks that target and use misconfigured network routing equipment pose an "imminent and real threat" to Internet security, according to a recent report by the federally funded CERT Coordination Center at Carnegie Mellon University in Pittsburgh.

Unlike denial-of-service attacks that involve individual servers, a router-based attack is harder to stop and could result in service disruptions across large swaths of the Internet.

"Routers, in essence, form the backbone of the Internet," said Kevin Houle, a member of CERT's team. "So attacks that involve routing equipment raise the potential of entire sections of the infrastructure being [disrupted]."

According to Houle, CERT has received an increasing number of reports of intruders taking unauthorized control of routers by using vendor-supplied default passwords. Once inside, such intruders could easily modify the router's configuration and protocol information to misdirect traffic over the Internet. Large sections of the network could be shut down by targeting critical routers, such as those belonging to a major service provider, Houle said.

"Once people start attacking routers in this manner, all hell will break loose," said K. Narayanaswamy, chief technical officer at Cs3 Inc., a Los Angeles-based security firm whose research in this area is partially funded by the Defense Advanced Research Projects Agency. "It's like taking the signs on a highway and pointing them in all the wrong directions."

This vulnerability involving routers has been known for a long time but assumed critical importance following the Sept. 11 attacks on the U.S. and the heightened threat of cyberterrorism, Narayanaswamy added.

Compromised routers can also be used by intruders to scan networks for vulnerable systems and as launch points for the more traditional denial-of-service attacks, which involve flooding a network with useless data, CERT warned. While misconfigured routers are the most vulnerable, intruders are also developing other ways of breaking into secure routers, according to analysts.


Generally, critical routers are much harder than Web servers to find, and therefore to attack, on a network, said Ted Julian, CEO of Arbor Networks Inc., a Waltham, Mass.-based vendor.

Unlike vulnerable servers, which are often found by automated scanning tools, breaking into routers requires more inside information and sleuthing work on the part of an intruder to identify the crucial routers to attack, Julian said. But if they are found and compromised, the resulting attacks could be "devastating," he said.

Although Arbor, like several other vendors such as Mazu Networks Inc. and Asta Networks Inc., sells tools to mitigate the effect of a denial-of-service attack targeting servers, there is little that is currently available to deal with router-based threats.

"There's not much you can do beyond making sure your own routers are secure [by changing default passwords]," said Edward York, chief technology officer at 724 Inc., an application hosting service in Lompoc, Calif. The company's servers have been hit with eight denial-of-service attacks this year alone, most of which it managed to handle on its own.

"This is a real threat that is going to be even harder for the authorities to stop," said Ralph Kuntz, chief technology officer at Hamilton Scientific Ltd., a Roseland, N.J.-based application service provider for health care providers.

One of Hamilton's routers was broken into earlier this year and was used to scan networks for vulnerable servers. The company learned of the compromised router only after receiving threatening letters from companies that had been scanned.

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